Nonlinear wave mixing via optical nonlinearities in optical media can be used to generate optical signals. For example, parametric four-wave mixing (FWM) utilizing high-Q microresonators can be used to generate optical frequency combs, which find a wide range of applications including spectroscopy, optical clocks, arbitrary waveform generation, frequency metrology, and astronomical spectrograph calibration. In various implementations of microresonator-based frequency comb generation, a system is optically pumped by an external continuous wave (CW) laser at a specific wavelength corresponding to a cavity resonance of the microresonator in which the FWM occurs. As pump power is coupled into the microresonator, thermal effects can shift the cavity resonance to higher wavelengths, thus creating a soft thermal lock between the cavity resonance and the pump laser. When the intracavity power exceeds the threshold for parametric oscillation, cascaded FWM and higher-order FWM processes occur, resulting in the generation of a frequency comb (i.e., a precisely spaced source of monochromatic frequency components).